1. Geog 463 GIS Workshop April 19, 2006

2. Outlines Overview of GIS operations Process diagram Geovisualization Spatial modeling Discussions

3. Part I. GIS operations

4. GIS operations Analysis is the core of GIS that transforms data into information Data manipulation operations –data availability  data readiness Data analysis operations –data ready to put into system  information INPUTOPERATIONSOUTPUT

5. Needs for data manipulation Incompatible cell sizes and boundaries confound multi-layer raster operations. These ambiguities are best resolved by resampling prior to layer combination Image source: Bolstad 2005

6. Data manipulation Data creation –Digitizing –Vectorization (ArcScan) Data editing –Topology editing (only in Arc/Info coverage and geodatabases) –Raster resampling (coregistering different raster images) Data conversion –Export/import (be aware of data loss due to incompatibility) Conversion among coordinate systems Coordinate transformation –Registration (control points) –Transformations –Rubber-sheeting

7. Examples of data manipulation Coordinate transformations Raster resampling Shift

8. Data analysis Queries Measurements Transformations Descriptive summaries Optimization Hypothesis testing Modeling Following Longley et al 2005

9. Queries (extract) Attribute queries –Select * from table where [condition] –Condition: logical expression –e.g. Median Age > 45 Spatial queries –Select * from layer where [condition] –Condition: based on spatial relationship –e.g. hospital within King County –e.g. hospital 10 kilometers farther from highway

10. Measurements Measure distance, area and parameter of a single feature –ArcToolbox or calculate fields –Use meaningful measurement unit (by converting geographic to state plane) –Make the use of ArcScript to measure more complex geometric properties on the ESRI website Measure slope and aspect of terrain –Work with DEM –ArcGIS Spatial Analyst

11. Transformations (vector) Simple spatial analysis that change datasets, combining them or comparing them to obtain new datasets Buffer Spatial overlay –Mostly translated into point in polygon operations e.g. # parcels within zoning area? –But there are an array of operations for polygon in polygon overlay with the added complexity (union, intersect, identity) Other commonly used –Clip, dissolve, erase, ….

12. dissolve union

13. Transformations (raster) Map algebra for raster –Local function (also known as reclassification) –Neighborhood function (focal function) filtering Spatial interpolation –Deterministic: IDW –Stochastic: Kriging –use Geostatistcal Analyst

14. Descriptive summaries Capture the essence of a dataset in one or two numbers Mean and standard deviation of attributes –It may not be included in the process diagram, but useful in gaining a overview of data and determining the appropriate data classification method for thematic mapping Descriptive summaries of spatial features –Mean center, dispersion (use CrimeStat) Measure spatial pattern of vector data –hot spot detection methods: nearest neighbor, K function… –Work with “point” data –ArcToolbox - Spatial Statistics Tools –Try CrimeStat by National Institute of Justice (freeware)

15. Optimization Problem-solving by optimizing objectives (minimize cost or maximize benefit) given constraints Finding the least cost path –Finding the best path based on link-node representation where cost information is attached Arc/Info workstation – dynamic segmentation, other software such as TransCAD, ArcView Network Analyst –Finding the gradient path based on grid data ArcGIS Spatial Analyst – least cost path Location-allocation problems –Location for a new retail store? –http://www.geog.ubc.ca/courses/klink/gis.notes/ncgia/u58.html#S EC58.1.2http://www.geog.ubc.ca/courses/klink/gis.notes/ncgia/u58.html#S EC58.1.2 Arc/Info workstation – location-allocation

16. Spatial modeling Definition 1: A sequence of different operations; aka. cartographic modeling (by Tomlin); process diagram –What if you want to change parameters and see what happens to outcomes? Want to automate the whole process? –Try Model Builder in ArcGIS: it allows you to run the whole procedures with one click Definition 2: Process model (extracted from previous knowledge) is embedded in operations so as to predict what would happen given input parameters –Range from simple mathematic model to process model Soil erosion = f (a, b, c, d); housing price = f (a, b, c, d) Hydrological modeling: sequence of logics or rules –Test what-if scenarios –Seek out for models developed by experts; do literature reviews!

17. How do I get help? Help file –Search by commonly used operation names –ESRI Library (manual) Software website –User Support, User Forum –Make the use of available scripts Previous work –Draw upon literature reviews –Web of Science for academic works –GIS magazines for professional works UW-gis-l list –To subscribe, uw-gis-l@u.washington.edu Instructors

18. Part II. Process Diagram

19. Process diagram

20. Determining criteria (factors)

21. Refining criteria General criteria Refined criteria (binary scheme) Refined criteria (continuous scheme) Slopes not too steep Slopes < 30 degrees For enough from road to provide privacy, but not isolated 300 meter < distance to road < 2000 meter

22. Determining weight

23. Part III. Geovisualization

24. Geovisualization Why do we use maps? Roles of map –Data exploration vs. map presentation –See Figure 13.5 from the assigned reading Why not utilize the more “interactive” environment provided by GIS? So as to facilitate thinking, understanding, and knowledge construction

25. Map presentation vs. data exploration Map presentation (Traditional cartography) Data exploration (Geovisualization) Interaction between map and user LowHigh Public or private realm PublicPrivate Information sharing or knowledge construction Info sharingKnowl. construction

26. The Geovisualization defined Creation and use of visual representations to facilitate thinking, understanding, and knowledge construction about human and physical environments, at geographic scales of measurement From MacEachren

27. What are advantages of geovisualization compared to traditional cartographic product? Query –You can make a simple geographic inquiry –See how message is sensitive to input data elements Transformation –Data can be manipulated such that objectives can be served better; it helps you overcome the limitation of traditional cartographic products (e.g. choropleth map) such as –Cartogram: areal size adjusted to magnitudes –Dasymetric map: spatial overlay Immersion –Expand the capacity to experience the world through virtual environment (3D representation of the world) –Data-rich environment (LiDar), Computing power (animation) –Facilitate distributed decision-making process

28. Iterative processes of spatial query Figure 13.6 (Longley et al p. 296) Real world Conception Measurement & representation Analysis Interpretation, Validation, Exploration Analysis (query) should not bee seen as an end point, but rather as the start of an iterative process of feedbacks and ‘what if?’ scenario testing feedback Example: population distribution by hard copy choropleth map versus geovisualization techniques

29. Geovisualization Foster greater user interaction and participation in the use of GIS as decision support tool User can undertake a balanced appraisal of the message of a geographic phenomenon; decision-makers can appraise the consequences of different representations Increasing role of users

30. Part IV. Spatial Modeling

31. Example: evacuation plan Identify high-risk area which is likely to be congested for the event of wildfire given a limited amount of time Congestion = f (network configuration, population density) What if we build the road with different design? What would happen? Planners can use the outcome of this simulation to design the road

32. Why model? In reality, it is impossible to experiment on the real world Instead, the model provides alternatives to experimenting on a digital replica of the world Allows us to evaluate the outcomes of different policy alternatives (i.e. “what-if scenario”) Can be used for dynamic simulation, providing decision makers with dramatic visualizations of alternative futures

33. Defining characteristics of model Involves multiple stages –How it will change over time Incorporate the previous knowledge –Approximation of reality –Some assumption on circumstance Experiment with scenarios or input parameters –Can compare different outcomes from varying scenarios or parameters

34. What are issues in building model especially in multicriteria method? Many decisions require the evaluation of multicriteria Different stakeholders is anticipated to have different views about what is important, how that importance should be measured, and how the various important factors should be combined e.g. problems of hazmat transport –Save money, save human life, save environment? wi: weight, xi: factors

35. Conflict resolution in multicriteria method Don’t negotiate alternatives Negotiate input parameters (what should be included as important criteria, and what relative importance is) Ideally, all of the controversy should be over once the factors, functions, and weights are decided, and the solution they produce should be acceptable to all, since all accepted the inputs. IDRISI (raster analysis s/w by clarklab) offers the extensive functionalities for multicriteria method

36. Discussion questions How is geovisualization different from a traditional cartography? Why do we build model given the fact that the model is an approximation of reality at best? What would be challenges and issues to consider in spatial modeling?